1. Field of the Invention
The present invention relates to an apparatus which aims at a plurality of minute points arranged on a plane and measures the intensity of each minute point, and more particularly to a fluorescent intensity measuring method and apparatus suitable for a system which aims at a bio chip in which substances such as DNAs or proteins labelled by a fluorescent substance are arranged on a plane as minute points with a high density and performs fluorescence analysis.
2. Description of the Related Art
For example, Jpn. Pat. Appln. KOKAI Publication No. 2000-121559 discloses an apparatus which measures a fluorescent intensity of each minute point.
FIG. 17 is a schematic block diagram showing a fluorescent intensity measuring apparatus disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2000-121559. The fluorescent intensity measuring apparatus disclosed in this publication is constituted by a chip drive portion 503 which scans in a direction Y in the drawing, a bio chip 520 in which samples subjected to fluorescence labelling are formed on a substrate surface as minute points, a laser 506 as an excitation light source, the laser beam is reflected by the mirror 580 toward a dichroic mirror 508 which reflects a laser beam from the laser 506 and transmits therethrough the fluorescence from the measurement object, a condenser lens 509, a head drive portion 502 which scans in a direction X in the drawing, a read head 507 including the condenser lens 509 and the dichroic mirror 508, a dichroic mirror 511 which separates the fluorescence from the minute points in accordance with each wavelength, filters 515 and 519 which separate the laser beam and the fluorescence, aperture lenses 514 and 518, pin-hole plates 513 and 517, and photomultipliers 512 and 516.
The effects of the fluorescent intensity measuring apparatus having such a structure are as follows. That is, the laser beam generated by the laser 506 is reflected by the mirror 580 toward the dichroic mirror 508 and is reflected by the dichroic mirror 508 and directed to the condenser lens 509. Then, it is condensed on the bio chip 520, thereby forming a laser beam spot. At this moment, when a fluorescent substance exists in a part irradiated with the laser beam spot, the fluorescent substance is excited by the laser beam, and the fluorescence is generated. The generated fluorescence is condensed by the condenser lens 509, then transmitted through the dichroic mirror 508, separated by the color separation dichroic mirror 511 in accordance with each wavelength, condensed by the aperture lenses 514 and 518 in accordance with each wavelength, transmitted through the pin-hole plates 513 and 517, and enters the photomultipliers 512 and 516. The photomultipliers 512 and 516 are sensors which detect photons and convert them into pulses on a TTL level, and hence the light which has entered the photomultipliers 512 and 516 becomes a pulse signal, and the fluorescent intensity of the minute point can be measured by measuring the pulse number. Further, if the above-described operation is carried out while mechanically scanning the laser beam spot by a chip drive portion 503 and a head drive portion 502, the fluorescent intensity of the minute points on the entire bio chip 520 is measured.
However, if foreign matter which reflects the excitation light or generates the fluorescence exists on the surface of the bio chip 520, the light which becomes the noise from the foreign matter is detected as well as the fluorescence from the spot 521 on the bio chip 520, and hence it is impossible to cope with occurrence of an error in the measured intensity.
Furthermore, since the prior art fluorescent intensity measuring apparatus cannot judge presence/absence of foreign matter, a quantitative judgment cannot be made with respect to the reliability of an intensity value of the minute points.
In view of the above-described problems, it is an object of the present invention to provide a fluorescent intensity measuring method and apparatus which can reduce measurement errors even if foreign matter exists in the vicinity of the surface of a bio chip, and can recognize the existence of foreign matter and make a quantitative judgment of the reliability of an intensity measurement value.